Process of manufacturing viscose rayon yarn



Dec. 30, 1947. A, .5, B OW 2,433,733

PROCESS OF MANUFACTURING VISCOSE RAYON YARN Filed Jan. 4, 1945zzvmvroze. fllfrea 5. Brawn Z? W HTTOIPNE) Patented Dec. 30, 1947 UNITEDSTATES PATENT OFFICE PROCESS OF MANUFACTURING VISCOSEv RAYON YARN AlfredS. Brown, Utica, N. Y., assignor to Skenandoa Rayon Corporation, Utica,N. Y., a corporation of Delaware Application January 4, 1945, Serial No.571,269

11 Claims. (Cl. 1854) rayon by the viscose process and more particularlyto the manufacture of viscose yarn of improved textile characteristics.

It has long been known that the strength of viscose rayon yarn isincreased by stretching the yarn during spinning, this increase instrength being enhanced if the stretching is performed while the yarn isbeing treated with hot water. In all viscose spinning systems, theviscose solution is extruded through a plurality of holes in a spinneretwhich is immersed in a bath containing perhaps eight to ten percent ofsulfuric acid. The action of this bath on the extruded viscose forms athread comprising a plurality of individual filaments, the thread beingdrawn through and out of this bath by some mechanical means. In two-bathviscose spinning systems the young thread emerging from the highly acidbath is then subjected to the action of a second bath containin perhapsone percent of sulfuric acid, this bath being maintained at an eleveatedtemperature in the range of 60C. to 100 C. The thread is often stretchedas much as 100 percent during its exposure to this second bath.

Numerous disclosures in the prior art are concerned with the details ofthe operation of twobath viscose spinning systems, as these details areof utmost importance in determining the textile qualities of theresultant yarn.

The provision of a viscose spinning process which improves the yarnstextile qualities is a primary object of this invention.

Another object of this invention is the provision of a viscose spinningsystem which improves the yarns textile qualities and still requiresonly a moderate exposure of the running yarn tothe several baths.

A further object of this invention is the provision of a process formaking a viscose rayon yarn the filaments of which are substantiallyhomogeneous.

An additional object of this invention is the provision of a process forimproving the effectiveness of the hot bath in two-bath viscosespinning.

An additional object of this invention is the provision of a process forretaining in the running thread the improved qualities imparted by thisnovel spinning system.

The attainment of these objectives is described in the followingspecification which also discloses still further objects of thisinvention.

I have found that the textile quality of viscose .2 yarn is material'yimproved when the twobath spinning system is so operated as to restrictthe stretching of the yarn to the time immediately after the yarnsemergence from the bath of the hot dilute acid, this improvement inquality being particularly great when a substantial length of therunning yarn in a relaxed state is wholly enclosed by the hot diluteacid of the second bath prior to any stretching of the yarn. I havefound, furthermore, that the accurate localization of the stretchingoperation is refiected in the yarns textile qualities in a surprisinglycritical manner.

These findings may be explained in terms of the cross-sectionalhomogeneity of the individual filaments in the yarn, although I do notwish to be limited to any particular theory of the observed effects ofthis invention. It is apparent that the reaction between the acid of thefirst bath and the viscose extruded through a spinneret hole must takeplace at the surface of the filament, producing a skin of regeneratedcellulose. Reaction between the acid and the generally interior regionsof the filament must await either the slow process of diffusion throughthis skin or the continued exposure of new surfaces by the slippage ofthe skin over the liquid interior of the filament, such slippage beingthe result of applying tension to the filament. Consequently the youngfilament has a chemical heterogeneity inherent in the presence of a skinand a generally unreacted interior, and has also a physicalheterogeneity in that the skin has been strained in carrying the runningtension. The production of a homogeneous filament must concern itselfwith the elimination of both chemical and physical strain differences.

The action of a very hot dilute acid on a young filament appears to bechiefly a relatively rapid regeneration of the cellulose in the interiorof the filament. Hence a short exposure of the young filament to such abath tends to make the filament chemically homogeneous in that the wholefilament rapidly becomes regenerated cellulose. If this completion ofthe spinning reaction takes place on substantially relaxed yarn, therewill be only a minimum of localized straining of the filamentscellulose, and subsequent stretching will operate uniformly over thecrosssection of the filament to produce a'stretched filament that isphysically as well as chemically homogeneous. As far as I have been ableto ascertain thecritical factors are: first, to keep the dilute acidbath very hot and in uniform contact with the filaments}; and second, torestrict any stretching of the filaments to a time after substantialcompletion of the action of the hot dilute acid.

This invention, then, may be described as a process of spinning viscoserayon wherein the -s. are formedin, a first bath. containin about 7 to10, percent; sulfuric acid; wherein the.

bundle of filaments is transferred to a second bath of hot dilute acidby positively driven means, exclusively, viz., without contacting anystationary or idling guide which woul'd'createany fric tional tension inthe thread; wherein the filaments are then subjected freely and in arelaxed state to the action of the hotdiluteacid; wherein the filamentsare lead from the second bath by,

positively driven means; and wherein after emergence from the secondbath the filaments. are given a first stretching, According to thepractice of this invention the run of the filaments in each bath needonly be moderate, distances of about 6 inches to about 25 inchesgenerally being sufficient, so that the need of elaborate and perhapseven harmful thread storage devices is eliminated. Furthermore, theamount of stretch imparted to the filaments is relatively low, a stretchof- 55 percent generally suificing to produce a yarn with a tenacity ofmore than 3 grams per denier; even though the viscose is prepared fromwoodpulp and the first: spinni'ngbath is of the simple, low zinc iontype.

Insofar as I am able to, ascertain, the theory axes in a vertical planeextending inside and parallel to the tank or trough l and longitudinalof the machine, the axes being, however, at a relatively small angle, inthe order of magnitude of about 8 to 25 to the vertical, so as toprovide a substantial distance of travel through the spinning bath 2.Prior to theemergence ofthe thread 6 therefrom. The wheel I ispositively driven at adesired speed by any suitable mechanism which isnot shown herein and which per se forms no part of the present,invention.

The thread 6 passes thence into a second bath 8,

, which is contained in a longitudinally extending explained above issubstantiated in that yarn made according to this new-processisexceptionally tough, and, on dyeing, appears to-have exceptionalcross-sectional homogeneity.

The practice of'my invention is more fully explained with reference tothe accompanying figures, wherein I also show certain additional processfeatures that I sometimes prefer to add to the; steps already described.

In the accompanying drawings there is shown in; more" or lessdiagrammaticf'orm a portion of a spinning machine, the details of-whiehform per se no part of the'present invention. In thedrawings:-

Figure l is adiagrammatic view; principally in plan, of a rayon yarnspinning machine, illustratingthe passage of the yarn through the twobaths above-referred to; and

Fig; 2 is a diagrammatic view principally: in vertical; section as seenfrom the-right'of Fig. 1'.

Referring; now to the accompanyingdrawings, I" have shown a trough l forliquid, comprising a first orspinning bath 2', Into thisbath extends aplurality-of pipes orgoosene-cks 3-, each of which has a spinneret 4 atits end beneath the surface of the spinningbath 2-. As indicated in Fig.1*, there are a number of similar units-arranged side by side along thelength of the machine, which may have any-desired number of such units;It willbe understood that viscose isforced through the i pipes orgoosenecks 3 and thence through the apertures in thespinnerets 4? inthe-usual manner and-by anysuitablemeanssuchasthose-nowconventional inthe art, The viscose is extruded through the several holes" in eachspinneret- 4* to form aplurality of filaments as-indicated at 5 beneaththe-surface offthespinnin bath 2; these frlaments collecting together toformv a single thread orstrand of yarn asshown generally at 6-: The yarn6 passes: fora substantial distance through the spinning bath 2toregenerate some of the cellulose of'thefilaments thereof, then emergestherefrom and passes around a Godet --wheel% L; These wheelsaredisposed' with their .troug-hQ-parallel-to and at about the samelevel as the bath .2' and the tank I. The liquid of this second bath maycontain substantially the same chemicals: as that of the spinning bath2, but is more, dilute than such spinning bath and, further, ispreferably maintained at a temperature in the range of about to C. Noheating means for the liquidin: the bath 8 are shown in the accompanyingdrawings, but it will be understood that the liquid thereof may beheated and maintained within a desired temperaturearange by the useofany suitable. means (not. shown). Within the bath. 8 the, running thread6' passes thence around av second Godet wheel H], which is arranged:with its axis substantially horizontally, and at a suitablev angle to'the bath so that the thread may be maintained thereon, and is positivelydriven ata: speed the same as or slightly slower than that of the wheel1'. The mechanism forsupportingand driving the wheel Id of each unit isnot. shown herein and; per se forms no part of the present invention;The wheels 1 and I 0 of each. unit are so disposed: and arranged inrespect to each other and in respect to the bath 8 that the thread Iivwill'haveta substantialiperiod of travel which I. sometimes. prefer tohave about 10" to- 20,- through the liquid Of'lihe bath 8 prior tocontactrwith anysoli-d body including the wheel H1, so asato permit.free access of the liquid in the'bath flfto all. of thefilaments of theyarn passing therethnoug-h inauniform: manner and thereby substantiallyto complete: the; regeneration of the cellulose of the filaments. Themaintenance of the liquid of thebath 8 at: elevated temperatures'supplies; heat to the thread or yarn during its passage therethrough'and tends to accelerate the chemical and physical reactions oroperationstaking place; so that the cellulose will be substantially completelyregenerated and, at the same time, will be: swelled to a certain extentwhich may tend to, cause a shrinkage of the yarn inlength. Tocompensatefor thistshrinkage, the wheel It may berun at asomewhat lower peripheralspeed than that of the: Wheel 1; However, it is desired as far aspossible; toprevent any substantial stretching of the; yarn betweenitsemergence from the'liquid of-fthezspinning bath' 2 and its. emergencefrom the'liquid of the bath 8. To this; end, thez thread; is preferablynot passed around any non-rotating guides byv which its directionischanged, nor isiti passed around any nonfpositively, driven rollers:in. the form of idlers as has. been customary: with. many prior artarrangements.

Oncethe' regeneration of: thercellulosehas been substantially'cornpletedin. a uniform manner as just described; it is now possible to stretch-ituni formly. For the purpose ofthis stretching, the yarn is passed fromthe Godet wheel It] around a third Godet wheel I 5, about which itpasses twice in a so-called"double= wrap;'passing around an intermediateguide l-2* to prevent crossing of the thread on this wheel. While I havechosen to show herein a double wrap around the Godet wheel II, this isnot always essential in practice. It will be understood that if but oneturn is taken around the wheel H, the guide l2 may be dispensed with.Again, the Godet wheel H is positively driven at a predetermined speedby suitable means (not shown).

The yarn passes from the wheel ll around a fourth Godet wheel l3 andthence downwardly through the usual funnel l4 to a spinning pot l5operated by a motor (not shown) in the conventional manner, this beingfor the present purposes a collecting point for the yarn. So far as thepresent invention is concerned the means I l-I5 may be considered as theconventional and known means now in commercial use in the pot or cakespinning of rayon, the pot l5 being rotated at a relatively high speed,and the funnel I4 being substantially vertically reciprocated bysuitable means (not shown) so as to build up a yarn bundle or cakewithin the pot H) which is removed from time to time by the machineoperator.

Intermediate the arrival of the yarn onto the periphery of the Godetwheel H and its point of leaving the fourth Godet wheel l3 the yarn maybe washed and cooled by the provision of suitable means such, forexample, as spray nozzles l6 and I1 directed toward the path of the yarnover wheels I I and I3, respectively, and adapted to sup-ply sprays ofcold water or other washing or treating liquids onto the yarn at thesepoints in its travel. The flow of water or other liquid through thespray nozzles l6 and I! may be respectively controlled by suitablevalves l8 and I9. I have also shown diagrammatically a collecting systemfor liquid sprayed onto the wheels 1 I and I3, comprising funnel means20 and 2|, drain tubes 22 and 23 and a receptacle 24 from which theliquid may be led off in any desired manner (not shown).

I also contemplate and under certain circumstances I may desire toeffect a certain amount of drying of the yarn during this portion of itstravel and thus preferably provide for this purpose an air nozzlegenerally indicated at 25, shown as directed onto the path of the yarnas it approaches its point of tangency with the periphery of the wheelI3. The air stream through the nozzle 25 may be controlled by a suitablevalve generally indicated at 26. This air is preferably controlled as totemperature and humidity, to predetermined points or ranges and may beat a temperature of about 75 F. and at a humidity substantially belowits saturation point, so as to effect a drying of the yarn. This dryinginvolves the evaporation of water from the yarn which has an inherenteffect of -cooling the yarn to a certain extent due to the latent heatof vaporization of the water evaporated. It will be understood, ofcourse, that in the event the air nozzle 25 is used for drying and/orcooling, the valve l9 will usually be cut ofi so that no water will besprayed onto the yarn through the spray nozzle l1; although the spraynozzle I 6 may be in operation simultaneously with the air nozzle 25.One way which I now propose to use this phase of the present inventionis to employ the air nozzles 25 of each unit for supplying to thespinning room the air which is normally supplied to such rooms, thus notonly humidifying the air in the spinning room, but also blowing this airdirectly onto the yarn for the aforesaid purpose.

From the above, it will be seen that I have provided a process by whichthe yarn is moved continuously along its path, passing solely over andaround positively driven wheels, rather than idlers or stationaryguides, with the single exception of the guide l2 used incident to thedouble wrap around the Godet wheel H. I have further provided a processby which the stretching of the yarn is specifically and substantiallysolely allocated to a desired part of the process, viz.,

after the substantial completion of the regeneration of the cellulose.The present process further provides for the regeneration of thecellulose to be carried substantially to completion in a uniform mannerby exposing the yarn for a substantial period of time in its path oftravel between the spinneret and the collecting point to the action of aheated dilute second bath, during a major part of this action the yarnbeing out of contact with any solid body, which might tend to interferewith the uniform chemical, physical, and thermal action of the liquid ofthis second bath upon the yarn. I further provide for the process stepsof washing and/or partial drying of yarn while cooling it subsequent tothe stretching operation and prior to its being passed to the collectingpoint. In this step of the process it may in some instances be preferredto provide for a certain amount of shrinkage in the length of the yarn.For this purpose the wheel I3 may be run at a somewhat lower peripheralspeed than that of the wheel II.

It will be understood by those skilled in the art that certain of thesefeatures have independent utility and some may be used without theothers, while some may be varied by'the substitution of other means orprocess steps within the knowledge of the art. I do not wish to belimited therefore, except by the scope of the appended claims, which areto be construed validly as broadly as the state of the prior artpermits.

What is claimed is:

1. In the manufacture of viscose rayon, the process which comprises thesteps of extruding at least one jet of Viscose into a spinning bath,comprising not over about 10% sulphuric acid, drawing the resultantbundle of at least one filament through said spinning bath by positivelydriven means to form a thread, passing this thread freely through asecond bath by positively driven means at substantially the same rate atwhich the thread is withdrawn from said spinning bath, wherebysubstantially no stretching takes place between said baths and duringthe passage of the thread through said second bath, said second bathcomprising a dilute acid bath which is at a temperature of about 60 toabout 100 C., and stretching the thread as it emerges from said secondbath.

2. The process in accordance with claim 1, wherein said spinning bathcomprises from about 7% to about 10% sulphuric acid, and wherein thecellulose is but partially regenerated in said spinning bath, andwherein said second bath comprises notover about 1%% sulphuric acid.

3. The process in accordance with claim 1; wherein the temperature ofsaid second bath is maintained at about to about C.

4. In the manufacture of viscose rayon, the process which comprises thesteps of extruding at least one jet of viscose into a spinning bath,comprising not over about 10% sulphuric acid, drawing the resultantbundle of at least one filament through said spinning bath by positivelydriven means to form a thread, passing this thread freely through asecond bath by positively driven means at a speed substantially the sameas the rate at which the thread is withdrawn: from-said spinning bath,whereby substan-- tially no stretching takes place between saidloathsand during the passage of the thread through said second bath,said second bath comprising a dilute acid bath which is at a temperatureof about 60 to about 100 C., and stretching the thread by apredetermined proportion of its length as it emerges from said secondbath by passing it thereafter around a third positively driven meansoperating at a peripheral speed a predetermined proportion greater thanthat of the second named positively driven means by which the thread isdrawn throu h said second bath.

5. In the manufacture of viscose rayon, the process which comprises thesteps of extruding at least one jet of viscose into a spinning bath,

comprising not over about 10% sulphuric acid, drawing the resultantbundle of at least one fil'a ment" through said spinning bath by passingit around a positively driven Godet'wheel and'thereby forming a thread,passing this thread freely through a second bath by passing it around asecond positively driven Godet wheel, Which is rotated at a speed suchthat the peripheral speed:

of said second Godet wheel is a predetermined proportion less than thatof the first named G'odet wheel, whereby the thread is permitted toshrink somewhat during its travel through said second bath, said secondbath comprising a dilute acid bath which is at a temperature of about 60to about 100 CL, and thereafter passing the thread from said secondGodet wheel to and around a third Godet wheel driven at a peripheralspeed a predetermined proportion faster than the peripheral speed ofsaid second Godet wheel to provide a predetermined controlled stretchingof the thread during its passage from said second to said third Godetwheel.

6. The process in accordance with claim 1, comprising the additionalstep of Washing the yarn subsequent to the stretching thereof aforesaid,and then passing the yarn to a collecting point.

'7. The process in accordance with claim 1, comprising the additionalstep of washing the yarn with cold Water subsequent to the stretchingthereof aforesaid and then passing the yarn to a collecting point.

8. The process in accordance with claim 1,

comprising the step of predetermining the stretching of the thread as itemerges from said second bath as aforesaid to limit such stretching tonot more than about 55% to about 60% of the length of the thread priorto such stretching.

9. In the manufacture of Viscose rayon, the process which comprises thesteps of extruding at least one jet of viscose into a spinning bath,comprising not over about 10% sulphuric acid, drawing the resultantbundle of at least one filament through said spinning bath by positivelydriven means to form a thread,' passing this thread freely through a,second bath by positively driven means at substantially the same rate atwhich the thread is withdrawn from said spinning bath, wherebysubstantially no stretching takes place between said baths and duringthe passage of the thread through said second bath, said second. bathcomprising a dilute acid bath which is at a temperature of about 60 toabout 100 C., stretching the thread as it emerges from said second bathby passing the thread from the second named positively driven means to athird 8-' positively driven means operating at a higher peripheral speedthan that of said second positively driven means, and controllablyrelaxing the thread subsequent to the stretching aforesaid by passingthe thread from the said third positively driven means to a fourthpositively driven means operating at a peripheral speed less than thatof said third positively driven means so as to relax the thread by apredetermined controlled amount.

19. The process in accordance with claim 9, comprisin the additionalstep' of washing the thread with cold water'during that portion of itstravel between its arrival on the third positively driven: means and itspassage from the fourth positively driven means.

11. In the manufacture of Viscose rayon, the process which comprises thesteps of extruding a plurality of jets of viscose into a spinning bath,comprising from about 7% to about 10% sulphuric acid, drawing theresultant bundle of filaments through said spinning bath by passing itaround a first positively driven Godet wheel and thus forming a thread,passing this thread freely through'a second bath which is at atemperature of about to about C. and which comprises not' over l /2%sulphuric acid by passing the thread around a second positively drivenGodet wheel partially immersed in said second bath, maintaining thespeed of rotation of said second positively driven Godet wheel such thatits peripheral speed is a predetermined proportion less than that ofsaid first Godet wheel so as to permit of a predetermined shrinkage inthe length of the thread during its passage through said second bath,controllably stretching the thread after it emerges from saidsecond bathby passing it directly from said second Godet wheel to a thirdpositively driven Godet wheel operating at a peripheral speed of notmore than about 55% to about 60% greater than theperipheral speed ofsaid second Godet wheel, controllably relaxing the thread subsequent tothe stretching thereof as aforesaid by passing it from said third Godetwheel to a fourth positively driven Godet wheel operating at aperipheral speed a predetermined proportion less than that of the thirdGodet wheel, cooling the thread during the controlled relaxing thereofby subjecting it to the action of cold water between its point ofarrival on said third Godet wheel and its point of leaving said fourthGodet wheel, and thereafter passing the thread to a collecting point.

ALFRED S. BROWN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,343,415 Polak May 9, 19%2,133,715 Parker Oct. 18, 1939 2,307,863 Soukup Jan. 12, 1943 1,996,989Bernstein Apr. 9, 1935 2,004,271 Dreyfus June 11, 1935 2,036,313Zimmermann et al. Apr. '7, i936 FOREIGN PATENTS Number Country Date515,127 Great Britain Nov. 27, 1939 813,762 France Sept. 14, 1938

